Intracellular Superoxide Dismutase Activity Research Articles

Effects of dietary β-glucan and glycyrrhizin on non-specific immunity and disease resistance of the sea cucumber (Apostichopus japonicus Selenka) challenged with Vibrio splendidus

Sea cucumbers, Apostichopus japonicus Selenka, were fed diets containing non-immunostimulant (basal diet), 0.2% β-glucan and 0.02% glycyrrhizin in a recirculatory water system for 45 days, and subsequently challenged with Vibrio splendidus by injection at 1.0×108 cfu / sea cucumber for 15 days. Phagocytic capacity (PC), intracellular superoxide anion production (ISAP), lysozyme (LSZ) activity and superoxide dismutase (SOD) activity in the coelomic fluid were analyzed on the 0th, 5th, 10th and 15th days after injection. Results showed that after the 45-day feeding period, PC, ISAP, LSZ activity and SOD activity in sea cucumbers fed with dietary β-glucan or glycyrrhizin were significantly higher than in those fed with the basal diet. On the 5th day after infection, all the immune parameters examined in the sea cucumbers injected with V. splendidus decreased in value significantly. On the 15th day, PC, ISAP and LSZ activity returned to levels similar to those on the 0th day. For the sea cucumbers injected with saline, there were no significant differences in all the immune parameters examined and in the cumulative morbidity during the 15-day challenging trial. After injecting with V. splendidus, the cumulative morbidity of sea cucumbers fed with the basal diet was significantly higher than those fed with dietary β-glucan or glycyrrhizin when challenged with V. splendidus challenged sea cucumber fed with the basal diet was significantly higher than those fed with dietary β-glucan or glycyrrhizin. There was no significant difference in cumulative morbidity between the dietary β-glucan and glycyrrhizin treatments over time.

The Protective Effects of the Active Fraction of Shaofu Zhuyu Decoction on Hydrogen Peroxide-Induced Oxidative Injury in Vascular Smooth Muscle Cells

In this paper, the protective effects of the active fraction (SF-7) from Shaofu Zhuyu decoction (SFZYD) were tested on a hydrogen peroxide (H2O2)-induced rat vascular smooth muscle cells (VSMCs) oxidative injury model. This active fraction (SF-7) shows potent antioxidant properties. The cell viability and oxidative damage markers of VSMCs were determined after exposure to H2O2 for 16 hours. It was observed that SF-7 significantly increased cell survival and reduced apoptosis of H2O2-injured VSMCs. Moreover, SF-7 could markedly increase intracellular superoxide dismutase (SOD) activity and decrease the malondialdehyde (MDA) level in H2O2-injured VSMCs, and suppress the generation of intracellular reactive oxygen species (ROS), as well as intracellular Ca2+ concentration. Thus, SF-7 exhibits protective effects against H2O2-injury on VSMCs, which may be associated with its antioxidant properties. It is suggested that SF may be useful in the treatment of blood stasis syndrome in which oxidative injury is mainly implicated.

Tissue Injury and Cellular Immune Responses to Cadmium Chloride Exposure in the Common Mussel Mytilus edulis: Modulation by Lipopolysaccharide

The immunotoxic effects of cadmium (Cd) exposure in bivalves are poorly understood and whether or not stimulation of the immune system exacerbates Cd toxicity is unclear. The mussel Mytilus edulis was exposed to 20 or 50 μg/l total Cd for up to 11 days compared to no added Cd controls to assess immune and other physiological responses. Selected experiments were then repeated in the presence of a lipopolysaccharide (LPS) challenge with and without subsequent Cd exposure. Immune functions of hemocytes, hematology, hemolymph glucose and ion content, as well as superoxide dismutase (SOD) activity and organ pathology were measured. Cd accumulated mainly in digestive gland and gills and to a lesser extent in the adductor muscle. Exposure to 20 μg/l Cd alone caused a transient modulated of phagocytosis and increased neutral red retention (Kruskal-Wallis, p = 0.002). The higher Cd concentration also increased cytotoxicity, and decreased hemocyte count. Changes in hemolymph Na(+), K(+), and glucose were small or negligible. Histopathological examination showed tissue injuries consistent with inflammation and necrosis in the gills, digestive gland, and adductor muscle during Cd exposure alone. LPS injection alone and LPS + Cd caused an increase in the number of circulating hemocytes by the end of the experiment (Kruskal-Wallis, p = 0.01) and a transient rise in phagocytosis at day 4 (analysis of variance (ANOVA), p = 0.001). The LPS + Cd treatment also caused transient changes in neutral red retention and in the cytotoxicity of hemocytes compared to controls. Intracellular SOD activity did not change in hemocytes under any treatment. Tissue inflammation and pathology was greatly increased by the effect of Cd exposure with an LPS injection compared to either treatment alone. We conclude that immunostimulation with LPS can greatly increase Cd-related organ pathologies but does not necessarily alter the responses of hemocytes.

Effects of Pretreatment by the Flavanol Ampelopsin on Porcine Kidney Epithelial Cell Injury Induced by Hydrogen Peroxide

This study investigated the protective effects of ampelopsin on H 2O 2-induced oxidative injury in porcine kidney epithelial cell line, PK-15; cells were pretreated with medium containing 0, 15, 30, and 60 μg mL −1 ampelopsin, respectively, for 1 h prior to the addition of 100 μmol L −1 H 2O 2. After 2 h, the cell viability, intracellular superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity, cellular malondialdehyde (MDA) content, and DNA strand breakage were determined. Results showed that ampelopsin pretreatment did not modify the SOD and GSH-Px inactivation but significantly decreased MDA production; except for the medium dose (30 μg mL −1), all the tested concentrations of ampelopsin did not significantly inhibit cell viability reduction and gave no influence on DNA damage. The results suggested that all the tested doses of ampelopsin pretreatment before H 2O 2 addition can protect PK-15 cell from H 2O 2-induced lipid peroxidation, which might not be mediated by the SOD and GSH-Px responsees. The appropriate dose of ampelopsin pretreatment prevents PK-15 cell from DNA damage and cell viability reduction.

Insufficiency of Copper Ion Homeostasis Causes Freeze-Thaw Injury of Yeast Cells as Revealed by Indirect Gene Expression Analysis

Saccharomyces cerevisiae is exposed to freeze-thaw stress in commercial processes, including frozen dough baking. Cell viability and fermentation activity after a freeze-thaw cycle were dramatically decreased due to freeze-thaw injury. Because this type of injury involves complex phenomena, the injury mechanisms are not fully understood. We examined freeze-thaw injury by indirect gene expression analysis during postthaw incubation after freeze-thaw treatment using DNA microarray profiling. The results showed that genes involved in the homeostasis of metal ions were frequently contained in genes that were upregulated, depending on the freezing period. We assessed the phenotype of deletion mutants of the metal ion homeostasis genes that exhibited freezing period-dependent upregulation and found that the strains with deletion of the MAC1 and CTR1 genes involved in copper ion homeostasis exhibited freeze-thaw sensitivity, suggesting that copper ion homeostasis is required for freeze-thaw tolerance. We found that supplementation with copper ions during postthaw incubation increased intracellular superoxide dismutase activity and intracellular levels of reactive oxygen species were decreased. Moreover, cell viability was increased by supplementation with copper ions. These results suggest that insufficiency of copper ion homeostasis may be one of the causes of freeze-thaw injury.

Response to oxidative stress ofCoriolus versicolor induced by exogenous hydrogen peroxide and paraquat

Effects of exogenous hydrogen peroxide (H2O2) and paraquat (PQ) addition on the oxidative stress response of white-rot fungusCoriolus versicolor were investigated. Water solutions of H2O2 and PQ were added to 7-day-old liquid cultures. The activities of extracellular ligninolytic enzyme, intracellular antioxidant enzyme and some biochemical parameters were determined up to 148 h after treatments. We found that the administration of 30 μM PQ and 6 mM H2O2 toCoriolus versicolor significantly stimulated the activities of manganese dependent peroxidase (MnP), lignin peroxidase (LiP), and laccases (LAC) in comparison to the control value (without PQ and H2O2). Administration of PQ and H2O2 also significantly enhanced expression of intracellular superoxide dismutase (SOD) and catalase (CAT) activities in the first 48 h. However, the response extent was different. PQ increased mainly ligninolytic enzymes, whereas H2O2 led to enhanced antioxidant enzymes. Concentration of phenolic compounds and formaldehyde (FA) increased with treatments, but the level of malondialdehyde (MDA) and H2O2 decreased with both treatments. The results indicate that exposure of the whiterot mycelia to PQ and H2O2 promoted oxidative stress. However, the antioxidant systems of the fungal strain are sufficient to prevent oxidative stress under PQ and H2O2 challenge. Exogenous reactive oxygen species (ROS), as an endogenous oxidative stress, may also be a useful substrate in microbial biodegradation of lignocellulose.

Protective Effect of Polysaccharide Fractions from Radix A. Sinensis against tert-Butylhydroperoxide Induced Oxidative Injury in Murine Peritoneal Macrophages

Three Angelica sinensis polysaccharide fractions (APFs), named APF1, APF2 and APF3, were isolated and purified from Radix A. sinensis and their antioxidant activities were evaluated in isolated mouse peritoneal macrophages by pretreatment with APFs before exposure to 0.2 mM tertbutylhydroperoxide (t-BHP). The results showed that pretreatment of the macrophages with APFs as low as 10 microg/ml could significantly enhance t-BHP-decreased cell survival, intracellular glutathione (GSH) content and superoxide dismutase (SOD) activity, and also inhibited t-BHP-increased lactate dehydrogenase (LDH) leakage and malondialdehyde (MDA) formation (p < 0.05), and APF3 was the most active fraction, followed by APF2 and APF1 in decreasing order. Furthermore, we found for the first time that the bound-protein in APF3 was associated closely with the protective effects and the polysaccharide inhibited the excess NO release from t-BHP-activated macrophages to protect host cells.

Improving the antioxidant activity of buckwheat (Fagopyrum tataricm Gaertn) sprout with trace element water

Trace element water (TEW) (100, 200, 300, 400 and 500ppm) was used to grow buckwheat (Fagopyrum tataricm Gaertn) to evaluate whether the beneficial effects of trace elements on the antioxidant activity could be accomplished with the supplement of TEW. At 300ppm, TEW significantly increased the Cu, Zn and Fe contents in buckwheat sprout, but not the Se and Mn contents. The levels of rutin, quercitrin and quercetin did not differ between buckwheat sprouts grown in TEW and de-ionized water (DIW). The ethanolic extract from buckwheat sprout grown in 300ppm TEW showed higher DPPH radical scavenging activity, ferrous ion chelating activity, superoxide anion scavenging activity and inhibitory activity toward lipid peroxidation than that grown in DIW. The extract of the TEW group also enhanced intracellular superoxide dismutase activity and resulted in lower level of reactive oxygen species in human Hep G2 cells.

Trace Element Water Improves the Antioxidant Activity of Buckwheat (Fagopyrum esculentum Moench) Sprouts

Buckwheat (Fagopyrum esculentum Moench) was grown in trace element water (TEW) (100, 200, 300, 400, and 500 ppm) and deionized water (DIW) to evaluate whether the beneficial effects of trace elements on the antioxidant activity could be accomplished with the supplement of TEW. At 300 ppm, TEW significantly increased the Cu, Zn, Mn, and Fe contents in buckwheat sprout but not the Se content. However, the levels of rutin, isoorientin, vitexin, and isovitexin did not differ between buckwheat sprouts grown in TEW and DIW. The ethanolic extract from buckwheat sprout grown in 300 ppm of TEW showed higher ferrous ion chelating activity and inhibitory activity toward lipid peroxidation than that grown in DIW. The extract in the TEW group also enhanced intracellular superoxide dismutase activity and lowered reactive oxygen species and superoxide anion in the human Hep G2 cell. It was concluded that TEW could increase the antioxidant activities of buckwheat sprouts.

Suppressing phosphatidylcholine‐specific phospholipase C and elevating ROS level, NADPH oxidase activity and Rb level induced neuronal differentiation in mesenchymal stem cells

In the previous research, we found that D609 (tricyclodecan-9-yl-xanthogenate) could induce human marrow stromal cell (hMSC) differentiation to neuron-like cells. In this study, to understand the possible mechanism, we sequentially investigated the changes of phosphatidylcholine-specific phospholipase C (PC-PLC) activity, the expression of Rb, the intracellular reactive oxygen species (ROS) levels, NADPH oxidase and superoxide dismutase (SOD) activities when D609 induced neuronal differentiation in rat mesenchymal stem cells (MSCs). The results showed that D609 obviously inhibited the activity of PC-PLC when it induced neuronal differentiation in rat MSCs. Simultaneously, ROS level and the activity of NADPH oxidase increased significantly, but the MnSOD and Cu/ZnSOD activities were not altered. Furthermore, the level of Rb protein was evidently elevated. Our data suggested that PC-PLC mediated neuronal differentiation of rat MSCs by elevating NADPH oxidase activity, ROS level, and up-regulating the expression of Rb protein.

Protective Effect of (-)-Epigallocatechin Gallate against Advanced Glycation Endproducts-Induced Injury in Neuronal Cells

Advanced glycation endproducts (AGEs) are believed to be secondary factors in the selective neuronal injury associated with several neurodegenerative disorders. In this study, we investigated the protective effects of (-)-epigallocatechin gallate (EGCG), a major monomer of green tea polyphenols, against AGEs-induced damage in neuron cells. The results showed that EGCG treatment protected against glyceraldehyde-derived AGE-induced neurotoxicity, which is associated with an increase in intracellular reactive oxygen species, as well as against decreases in intracellular catalase (CAT) and superoxide dismutase (SOD) activities. EGCG treatment also decreased malondialdehyde and carbonyl levels, and AGEs formation. Treatment with 10 muM EGCG upregulated SOD and CAT levels, whereas glutathione peroxidase activity was reduced. Furthermore, 5 muM EGCG was found to down-regulate the mRNA level of the AGE receptor (RAGE) in neuronal cells up to 2.5 fold, as determined by real time PCR. The results demonstrated that EGCG may exhibit protective effects against AGEs-induced injury in neuronal cells through its antioxidative properties, as well as by interfering with AGEs-RAGE interaction mediated pathways, suggesting a beneficial role for this tea catechin against neurodegenerative diseases.

Ligninolytic enzymes can participate in a multiple response system to oxidative stress in white-rot basidiomycetes: Fomes fomentarius and Tyromyces pubescens

Abstract The effect of menadione (MQ; 2-methyl-1,4-naphtoquinone) superoxide generating agent on the biological activity of two strains of white-rot fungi, Fomes fomentarius and Tyromyces pubescens, was determined. In this study 1 mM of MQ solution was added to 10-day-old idiophasic cultures. The application of MQ to F. fomentarius and T. pubescens cultures stimulated extracellular laccase (LAC) and manganese-dependent peroxidase (MnP) activities in comparison to the control values (without MQ). In the presence of MQ the concentration of oxalic acid in the medium of both fungi was dramatically decreased. MQ treatment also caused an increase of intracellular superoxide dismutase activity, formaldehyde and glutathione disulfide level in both strains. In the case of F. fomentarius, addition of MQ enhanced catalase activity. The rate of intra- and extracellular proteolysis decreased in F. fomentarius and increased in T. pubescens MQ treated cultures.

Xanthine oxidase‐derived free radicals directly activate rat pancreatic stellate cells

Free radicals are reported to be associated with fibrosis in the pancreas. It is generally accepted that pancreatic stellate cells (PSC) play an important role in pancreatic fibrosis. However, the exact role of free radicals in activation of PSC has not been fully elucidated. In the present study, using a superoxide dismutase (SOD) inhibitor, diethyldithiocarbamate (DDC) with cultured PSC, we investigated how free radicals act on the activation of PSC. PSC were isolated from male Wister rats. Cultured rat PSC were incubated with DDC for 48 h. Intracellular SOD activity and lipid peroxidation were examined in DDC-treated PSC. Activation of PSC was examined by determining the expression of alpha-smooth muscle actin (alpha-SMA) by immunocytochemistry. The number of PSC using a hemocytometer, type I collagen secretion with ELISA and matrix metalloproteinases (MMP) activities with gelatin zymography were also examined. Secretion of transforming growth factor-beta1 (TGF-beta1) was evaluated by ELISA. The effects of the allopurinol, a xanthine oxidase (XOD) inhibitor, on PSC were also examined. DDC decreased SOD activity and increased lipid peroxidation products in PSC. DDC activated PSC, increasing the number of alpha-SMA positive cells, enhancing secretion of type I collagen and MMP, inhibiting PSC proliferation. Secretion of TGF-beta1, which is known to activate PSC, was increased by DDC treatment. These alterations were prevented by allopurinol. These results suggest that free radicals generated by XOD might directly activate PSC.

Improved anti-oxidant activity of superoxide dismutase by direct chemical modification

Chemically modified derivatives of superoxide dismutase (SOD), i.e., cationized (Cat-SOD) and mannosylated SOD (Man-SOD), were designed to improve an ability of SOD to suppress reactive oxygen species (ROS)-mediated injury in the alveolar epithelium. To evaluate their effectiveness, an in vitro model of paraquat poisoning was developed with primary cultured rabbit alveolar type II cells. Despite a 5.6-fold higher cellular association than native SOD, Man-SOD did not protect cell injury due to paraquat following evaluation by MTT assay. In contrast, Cat-SOD exhibited a 140-fold higher cellular association than native SOD and greatly suppressed paraquat-induced cell injury, as well as lipid peroxidation. Incubation with 300 U/ml Cat-SOD for 2 h increased intracellular SOD activity 5.3-fold. The increase in intracellular SOD activity was significantly inhibited in the presence of cytochalasin B, an endocytosis inhibitor. Internalization of Cat-SOD was also confirmed by confocal laser scanning fluorescein microscopy. In addition, the protective effect of Cat-SOD against paraquat-induced cell injury was completely abolished by the presence of cytochalasin B. In conclusion, this study demonstrated that cationization of SOD greatly enhances its intracellular delivery and, as a consequence, produces a significant protective effect against ROS-mediated injury of the alveolar epithelium.

Acid stress adaptation protects Saccharomyces cerevisiae from acetic acid-induced programmed cell death

In this work evidence is presented that acid stress adaptation protects Saccharomyces cerevisiae from acetic acid-mediated programmed cell death. Exponential-phase yeast cells, non-adapted or adapted to acid stress by 30 min incubation in rich medium set at pH 3.0 with HCl, have been exposed to increasing concentrations of acetic acid and time course changes of cell viability have been assessed. Adapted cells, in contrast to non-adapted cells, when exposed to 80 mM acetic acid for 200 min did not display loss of cell viability associated to morphological alterations typical of apoptosis. Thus, 80 mM acetic acid death-inducing conditions were selected to further characterize the early molecular events leading to such active cell death process. Catalase was specifically activated during acid stress adaptation and protection against acetic acid-induced death was associated with maintenance of its activity during treatment with 80 mM acetic acid. On the other hand, intracellular superoxide dismutase activity was found present at comparable levels both in adapted and in dying yeast cells, excepting in non-adapted cells which displayed a maximum activity value after 15 min acetic acid exposure, corresponding to more than 80% cell viability. This study gives first experimental evidence that H 2O 2, rather than superoxide, detoxification may have a major role in preventing yeast cell death in response to acetic acid. The results, as a whole, suggest that commitment of S. cerevisiae to a programmed cell death process in response to acetic acid is mediated through a ROS-dependent apoptotic pathway.

Gleditsia sinensis fruit extract-induced apoptosis involves changes of reactive oxygen species level, mitochondrial membrane depolarization and caspase 3 activation

Recently, we have shown that the anomalous fruit extract of Gleditsia sinensis (GSE) processes apoptotic activity on numerous solid tumour and leukaemia cell lines as well as primary cultured leukaemia cells obtained from bone marrow aspirate of patients. GSE treated cancer cells exhibited apoptotic features as readily illustrated by morphological investigation, DNA fragmentation analysis and TUNEL labelling methods. Elevation of intracellular superoxide dismutase activity was observed. However, the detailed mechanism still remains undefined. Here we further demonstrated that cell cycle arrest, increment of hydrogen peroxide production, changes of intracellular acid-base equilibrium and mitochondrial membrane potential depolarization (DeltaPsi(m)) were induced from cancer cells after GSE incubation. Caspase 3 protease activity was significantly enhanced upon GSE treatment. Taken together, a defined signaling pathway for the mechanistic action of GSE on cancer cells was worked out.

Variations in metal uptake, antioxidant enzyme response and membrane lipid peroxidation level in Fusarium equiseti and F. acuminatum

The relationship between metal uptake, antioxidant enzyme activities, and membrane lipid peroxidation level (LPO) in Fusarium equiseti and F. acuminatum grown in media with different iron and manganese concentrations was investigated with respect to incubation period. Increasing the iron concentration (1–20 μM) in the culture medium of the Fusarium species resulted in steady increases in intracellular iron levels and steady decreases in magnesium and zinc levels, whereas intracellular manganese levels rose until Fe 2+ concentration reached 3.7 μM and decreased significantly at 20 μM Fe 2+. Intracellular manganese and magnesium levels increased with respect to increase in manganese concentration (2.5–30 μM) of the culture medium although zinc level did not change significantly. Intracellular iron levels increased up to an Mn 2+ concentration of 5.9 μM and then decreased with further increase in manganese concentrations as well as the response of iron. Superoxide dismutase (SOD) activities of both of the Fusarium species reached their maximum values at 3.7 μM Fe 2+ at which concentration intracellular manganese contents also increased. At higher iron concentrations in the medium, intracellular manganese levels and SOD activities decreased while iron contents continued to increase. Catalase (CAT) activities of these Fusarium species reached their respective maximum values at 3.7 μM Fe 2+. The highest levels of SOD and CAT activities of F. equiseti and F. acuminatum were found in the medium containing 5.9 μM Mn 2+ except for SOD activity of F. acuminatum which had a maximum value in the medium containing 30 μM Mn 2+. As an indicative marker of oxidative damage, LPO levels of both Fusarium species showed negative correlation with SOD and CAT activities. Maximum LPO levels were found where minimum antioxidant enzymes and maximum iron contents were observed in the cells.

Alterations in intracellular and extracellular activities of antioxidant enzymes during suspension culture of sweetpotato

Cultured plant cells are a good system for the study of antioxidant mechanisms and for the mass production of antioxidants, because they can be grown under conditions of high oxidative stress. Alterations in the intracellular and extracellular activities of three antioxidant enzymes, superoxide dismutase (SOD), guaiacol-type peroxidase (POD), and glutathione peroxidase (GPX), were investigated in suspension cultures of sweetpotato ( Ipomoea batatas) during cell growth. Intracellular SOD activities (units/mg protein) at 15 days after subculture (DAS) and 30 DAS were 10 and 20 times higher, respectively, compared with the SOD activity at 1 DAS, whereas intracellular specific POD and GPX activities did not significantly increase until after 15 DAS, when they rapidly increased. The extracellular activities of the three enzymes in culture medium were much higher than were the intracellular activities. The change in extracellular SOD activity was similar to that of extracellular GPX during cell growth. Those activities showed high levels until 5 DAS and then significantly decreased. Extracellular POD activity had an almost constant level regardless of the cell growth stage. In addition, intracellular SOD and POD isozymes were quite different from those isozymes in the culture medium. The changes in SOD and POD isozymes observed here suggest that different isozymes might modulate the levels of reactive oxygen intermediates during cell growth. Characterization of extracellular antioxidant enzymes discovered here would provide a new understanding for defense mechanism in plants.

Superoxide dismutase activity enhanced by green tea inhibits lipid accumulation in 3T3-L1 cells.

We studied the effect of powdered green tea on intracellular superoxide dismutase activity in the adipose conversion of 3T3-L1 cells. By the 14 days of culture with insulin, the triglyceride concentration was increased. When powdered green tea and insulin were added simultaneously, the increased triglyceride content was decreased (p < 0.05), and the superoxide dismutase activities were significantly enhanced (p < 0.05). These data suggest that green tea may have an antilipogenic activity due to its radical scavenging activity mechanism.

Expression of Prion Protein Increases Cellular Copper Binding and Antioxidant Enzyme Activities but Not Copper Delivery

The N-terminal region of the prion protein PrP(C) contains a series of octapeptide repeats. This region has been implicated in the binding of divalent metal ions, particularly copper. PrP(C) has been suggested to be involved in copper transport and metabolism and in cell defense mechanisms against oxidative insult, possibly through the regulation of the intracellular CuZn superoxide dismutase activity (CuZn-SOD) or a SOD-like activity of PrP(C) itself. However, up to now the link between PrP(C) expression and copper metabolism or SOD activity has still to be formally established; particularly because conflicting results have been obtained in vivo. In this study, we report a link between PrP(C), copper binding, and resistance to oxidative stress. Radioactive copper ((64)Cu) was used at a physiological concentration to demonstrate that binding of copper to the outer plasma cell membrane is related to the level of PrP(C) expression in a cell line expressing a doxycycline-inducible murine PrP(C) gene. Cellular PIPLC pretreatment indicated that PrP(C) was not involved in copper delivery at physiological concentrations. We also demonstrated that murine PrP(C) expression increases several antioxidant enzyme activities and glutathione levels. Prion protein may be a stress sensor sensitive to copper and able to initiate, following copper binding, a signal transduction process acting on the antioxidant systems to improve cell defenses.